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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Sunday, September 3, 2023

SPC Sep 3, 2023 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Sep 03 2023 Valid 031300Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF EASTERN NEVADA AND WESTERN UTAH... ...SUMMARY... Isolated severe gusts and hail are possible across much of the Intermountain West this afternoon and evening. Severe gusts may concentrate over parts of eastern Nevada and western Utah. ...Synopsis... The mid/upper-level pattern will become much more progressive over the western CONUS, as an initially cut-off low near Cape Mendocino devolves to a strong, open-wave trough and shifts inland. By 00Z, the trough should extend from eastern OR southward across the central/northern Sierra to coastal southern CA. By 12Z, it should reach southwestern MT, southeastern ID, and the eastern border of NV. The mid/upper trough should be preceded by a related low-level cold front moving eastward across the Great Basin toward the central/northern Rockies. The 00Z front should be located across central MT, western WY, northwestern UT, and central NV. By the end of the period, this front should extend from a low over western ND southwestward through the central Rockies to southern UT, with a lee trough southward over the central High Plains. As the mid/upper trough advances eastward, the longstanding high/ ridge over the south-central Plains will weaken. However, the cut-off low now over north TX will remain too far from associated height falls for any substantial influence until day 2, and in the meantime, will meander erratically near its present position. General thunderstorm potential will continue in an area of favorable low-level moisture and difluent mid/upper winds from near the low to its east and southeast, across the lower Mississippi Valley and portions of the Gulf Coast States. ...Intermountain West... Widely scattered to scattered thunderstorms are possible along/ahead of the cold front this afternoon into evening, as an expansion/ extension of ongoing, initially nonsevere activity over northwestern NV and southeastern OR. Isolated severe gusts and perhaps hail could be observed almost anywhere over a vast area of the Intermountain region and Great Basin. Within that, a relative concentration of severe-gust potential in particular appears possible across parts of northwestern UT and eastern NV. A longstanding plume of moisture advection/transport from subtropical latitudes, contributing for extensive convective activity and precip the past few days over swaths of this area, will persist and even expand today, under increasing influence from the accelerating mid/upper trough. Large-scale lift -- both from warm advection and DCVA -- will destabilize the mid/upper levels somewhat, with already weak MLCINH essentially vanishing in areas that can experience sustained diurnal heating. A midlevel dry slot evident in satellite imagery may foster such destabilization over parts of eastern NV/western UT, with resultant convection moving northeastward over somewhat well-mixed boundary layers of lower ground elevations. Modified model soundings suggest peak MLCAPE in the 800-1300 J/kg range over the 15% wind area, amidst 35-45 kt effective-shear magnitudes. As such, a blend of supercells and multicells is possible, with some clustering of the latter further contributing to local wind potential. Isolated large hail also will be possible, mainly with any sustained supercells. ..Edwards/Leitman.. 09/03/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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